2017 Volume 64 Issue 1 Pages 1-10
Two harmful red tide causative raphidophytes Chattonella antiqua (Hada) Ono and C. marina (Subrahmanyan) Hara & Chihara occurred in Isahaya Bay, Japan in 2007. A mesocosm was installed in Isahaya Bay where outbreaks of Chattonella red tides (103–104 cells mL-1) have frequently been observed. In order to examine the controlling factor of the diurnal vertical migration of Chattonella spp., vertical profiles of water temperature, salinity, chlorophyll fluorescence, concentration of DIN, PO4-P and cell density of Chattonella spp. were continuously measured in the mesocosm during two periods (8–9 and 23–24 August in 2007). These data indicated two vertical profile types of Chattonella spp. For one type, cells of Chattonella spp. vertically migrated to the lower layer in shallower waters, and its cell density reached more than 103 cells mL-1. For another type, cells of Chattonella spp. continuously aggregated more than 104 cells mL-1 in the upper layer (0.5–2.0 m depth) until a night without the diurnal vertical migtation (moving to deeper waters during the day) in the condition of a sufficient nutirient in the upper layer (DIN: >1 µM, PO4-P: >0.1 µM).
